The present invention relates to a phase difference plate for a circularly polarizing plate, particularly to a phase difference plate for a circularly polarizing plate that has an optically anisotropic layer containing a helically aligned liquid crystal compound.
The present invention also relates to a circularly polarizing plate or an organic electroluminescence (EL) display apparatus that has the phase difference plate for a circularly polarizing plate.
Phase difference plates are extremely versatile and are used for reflective LCDs, transflective LCDs, brightness enhancement films, organic EL display apparatuses, touch panels, and the like. For example, since organic EL devices have a structure in which layers having different refractive indices are laminated on each other or a structure which uses metallic electrodes, external light is reflected from the interfaces between the respective layers, and this leads to problems such as a decrease in contrast or reflection in some cases. Therefore, conventionally, in order to suppress negative effects caused by the reflection of external light, a circularly polarizing plate constituted with a phase difference plate and a polarizing film is used for organic EL display apparatuses, LCD display apparatuses, and the like.
Regarding a phase difference plate used for a circularly polarizing plate, for example, as described in JP 3174367 B, the use of a phase difference plate constituted with a λ/2 plate and a λ/4 plate is known.